The cortical control of visually guided saccadic eye movements involves of two major systems, the anterior and the posterior. The anterior system, comprised of the frontal eye fields (FEF) and the dorsomedial frontal cortex (DMFC), has direct access to brainstem oculomotor centers. The posterior system, comprised of several regions of the occipital and parietal cortices, does not appear to have direct access to the brainstem; for the most part it reaches these centers either through the superior colliculus or through the frontal lobe. The major focus of the proposed work is to understand the manner in which these two cortical systems control visually guided eye movements, how they differ from each other and how they interconnect. Behaving rhesus monkeys will be studied using recording, electrical microstimulation, reversible inactivation, and lesion methods. Part of the work will utilize chronic multiple single-cell recordings that will enable us to study neuronal properties over extended time periods to study organizational changes in individual neurons. We have devised an extensive battery of tests, some of them new, to study the visual and visuo-motor capacities of animals. One of these tests that utilizes dual targets presented with various temporal asynchronies. will be used to study the extinction phenomenon both in monkeys and patients with brain damage to the anterior and posterior eye-movement systems. The proposed research will increase our knowledge of the neural control of eye and limb movements and will allow us to compare these systems in monkeys and humans.